Traffic-related information can in particular be traffic signs which for example indicate the highest permitted speed. Alongside explicit traffic signs, the invention relates however to all information which can be received, visual or otherwise such as via radio, and which specifies a certain manner of driving, such as a speed which must be observed. It is provided that the image data of a visual sensor, in particular of a visual camera which is pointed in the driving direction, and the card data of a navigation system, are respectively pre-evaluated for recognition purposes, and the results of the pre-evaluation are compiled and interpreted.
Many developments in modern motor vehicles serve to draw the attention of the driver to traffic-related information in order to make driving safer overall. This includes in particular information regarding the current valid maximum speed, which alongside purely auxiliary information for the driver can also be used to generate warning messages or for direct interference in the speed of the motor vehicle by braking or accelerating.
For many years, navigation systems have been known in which alongside the course of the road and road type, a speed limit which is relevant in each case is also entered. The quality of this speed limit, which is firmly entered into the road maps, depends to a significant degree on the completeness and current relevance of the digitalised maps, however. After a speed limit has been changed, experience has shown that it takes a long period of time until new speed information is entered into the digital maps. A far greater problem is that the digital road maps are frequently stored in the navigation systems, and experience has shown that they are relatively infrequently updated by the user, since this entails not insignificant costs.
It is even more difficult with regard to the system to capture temporary information which is provided for example by sign bridges on motorways with information which has been adjusted to the traffic flow and speed limits, or on building sites. It is precisely this temporary information which is of particular relevance to safety, since the speed limits or other rules given to the driver of a motor vehicle in this manner have been adjusted to the current traffic flow or an acute hazard situation. However, this information cannot be captured by the navigation system described above.
For this purpose, DE 199 38 261 A1 recommends that temporary local conditions or personal impressions by the driver which are related to the route be taken into account, in which temporary local conditions which can be entered automatically or manually such as temporary speed limits, traffic jam warnings or similar can be set as variable electronic route markers, which are shown when the route is traveled repeatedly and/or have a regulatory influence on the automatically regulated operation of the motor vehicle. The particular problem here, however, is that this information is usually available only when the route is traveled again, and cannot be retrieved precisely in situations when the driver is travelling an unknown route for the first time.
DE 199 38 267 A1 recommends a system for the electronic recognition of traffic signs which are captured by means of a video camera, subsequently interpreted and displayed inside the motor vehicle. The recognised traffic signs should be stored in a navigable, electronic route map in relation to the location in order to improve the quality of the digital map and to enable improved correlation of traffic signs with navigable route data. As a supplement, it is recommended by DE 199 38 266 A1 for this purpose that when there is no doubt-free recognition of a traffic sign or of one of several traffic signs, a logical consideration be automatically made of such a type that further traffic flow parameters and/or traffic signs are included in the interpretation, and that as a result, the most minimal speed limit possible is calculated. This data is stored in correlation with the location, wherein the driver is given the option of correcting it.
DE 103 54 910 A1 discloses an autonomous motor vehicle which is equipped with a self-controlling navigation system and which monitors traffic signs which are set up on the edge of the road. For this purpose, a camera records traffic signs which are set up along the motorway. An image processor analyses these images and calculates the symbol content contained in the traffic signs. At the same time, map information regarding the motorway is stored in a navigation database. An electronic control unit with artificial intelligence now calculates a present position of the independently driven motor vehicle and a road condition on the basis of the map information stored in the navigation database and the symbol content read by the image processor. Building on the result of the calculations, a processor then controls a steering operation, a speed reduction/increase operation and an operation which is connected to the self-control navigation operation. This system is initially restricted to motorways, however, since there, the symbols used are limited and an interpretation and recognition of these symbols is far easier than on many other roads, in particular in towns and cities where the signs are frequently unclear.
EP 1 114 371 B1 describes a method and a device for recognising traffic signs and navigation. When traffic signs are recognised, traffic sign recognition data is created and navigation data provided for the purpose of localising the motor vehicle, wherein the traffic sign recognition data and the navigation data is mutually adjusted and if necessary updated. For this purpose, this data is fed to a shared evaluation unit which calculates a currently valid speed limit and if necessary, generates control signals.
All the systems described above have the problem, however, that the data gained as a result of image data recognition is very comprehensive and the data processing described frequently cannot be conducted in real time, at least when all image data is evaluated accordingly.
For this reason, EP 1 145 186 B1 recommends a system with at least one map-based navigation system and a system for displaying content by means of traffic signs which are recorded by a camera, in which the system for recognising traffic signs starts to operate with increased capacity when on the basis of map-based information, it is realised that the motor vehicle is passing an area which is problematic with regard to the recognition of traffic signs. For this purpose, a multi-processor system is used for the utilisation of free data capacity in the entire motor vehicle. Here, however, the problem is that the increased computing capacity is only provided when information is only present for the fundamental map-based system regarding the fact that a situation could arise which is possibly difficult to evaluate for the image capturing.